[llvm] [BranchFolding][RISCV] Optimize branches NE/EQ to zero or one (PR #131684)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> Nice work! It's great to see this finally fixed.
> 
> Just one question: have you consider implementing this in `RISCVInstrInfo::optimizeCondBranch`?
> 
> It's only used here:
> 
> https://github.com/llvm/llvm-project/blob/4f7dc99a8a3e34e925ef66e7069b01b811e837ba/llvm/lib/CodeGen/PeepholeOptimizer.cpp#L1793
> 
> but I wonder if we could get more cases covered by changing `optimizeCondBranch` (instead of the new `trySimplifyCondBr`) + your changes to `RISCVInstrInfo::analyzeBranch`.
> 
> I'll run SPEC with your patch tonight, we should have the results tomorrow morning

Let me see if I can use optimizeCondBranch and post an update here.

You should run spec with https://github.com/llvm/llvm-project/pull/131728 instead of this patch because we will clean up more cases.

https://github.com/llvm/llvm-project/pull/131684